[lammps-users] A query about input script

Hi all,
       I am new to LAMMPS and i am trying to perform to biaxial molecules on higher density.
In the output listed while perform, i found that the pressure is having a negative value.
I tried to perform only NVT simulations the pressure term displays a negative value.i know the system shrinks 
Could you please kindly let me know why is it and how to stop the shrinking of system . Herewith i have attached my input script and log file
Kindly let me know what can i do.

# ------------------------------------------------------------------------------
# ----------- GayBerne ellipsoids in a 3D  -------------------------------
# ------------------------------------------------------------------------------
units             lj
atom_style        ellipsoid
dimension         3
boundary          p p p

lattice            sc 0.30
region             box block 0 10 0 10 0 10
create_box        1 box
create_atoms      1 box

set               type 1 mass 1.0
set               type 1 shape 1.4 0.714 3.0

set               type 1 quat 0.892 0.09 0.095 0.367

pair_style      gayberne  1.0 3.0 1.0 4.0
pair_coeff  * * 1.0 0.710 1.7 1.2 0.2 1.7 1.2 0.2 4.0

[log.bxl3|attachment](upload://fOAElqzK3unP599gHrDOWdIK5XB.bxl3) (9.31 KB)

Please note that most of your questions are actually not questions about LAMMPS but about understanding the physics of MD simulations (i.e. mostly statistical mechanics and statistical thermodynamics) and how you apply that knowledge to your specific system. that makes it less of a topic for this mailing list, but should be discussed with your adviser/supervisor/tutor or more experienced colleagues.

Please also note that you have to pay closer attention to responses you get. I told you that “the system wants to shrink”, and not that it shrinks. there is a big difference. you can easily confirm that by outputting the volume in a custom thermodynamic output.

Now what to do about this is another topic for a discussion with your tutor/adviser/supervisor/colleagues. If you had the suitable training already that is a requirement to do proper MD simulations, you would already know what to do.I can give you a quick “change this to that” type of answer, but that would not give you the understanding you need to make fewer mistakes when it comes to more complex problems.